Tomographic image forming apparatus and control method

Abstract

A tomographic image forming apparatus is disclosed, which divides light output from a light source inside the apparatus into measurement light and reference light, and which generates a cross-sectional image of an imaging target, based on light intensity of interference light obtained from reflected light obtained by emitting the measurement light to the imaging target and the reference light. A second image is generated by converting a first image in which line data generated based on the light intensity and having information in a direction of a first axis which serves as a depth direction of the imaging target is arranged in a direction of a second axis, into a frequency domain. An artifact is removed or reduced by performing filtering on the second image. A third image is generated by inversely converting the processed second image into a spatial domain.

What is claimed is: 
     
       1. A tomographic image forming apparatus which divides light output from a light source inside the apparatus into measurement light and reference light, and which generates a cross-sectional image of an imaging target based on light intensity of interference light obtained from the reference light and reflected light obtained by emitting the measurement light to the imaging target, comprising:
 a processor configured to:
 generate a second image by converting into a frequency domain a first image in which line data being generated based on the light intensity and having information in a direction of a first axis showing a depth direction of the imaging target is arranged in a direction of a second axis; 
 remove or reduce an artifact by performing filtering on the second image; and 
 generate a third image by inversely converting the second image into a spatial domain. 
 
 
     
     
       2. The tomographic image forming apparatus according to  claim 1 , wherein the first image is converted into the second image by Fourier transform, cosine transform, or sine transform. 
     
     
       3. The tomographic image forming apparatus according to  claim 1 , wherein the processor is configured to:
 reduce an amplitude of a DC component which shows a zero frequency on the second image, compared to other components. 
 
     
     
       4. The tomographic image forming apparatus according to  claim 1 , wherein the processor is configured to:
 reduce an amplitude of a DC component, which shows a zero frequency in at least one axial direction on the first image, on the second image, compared to other components. 
 
     
     
       5. The tomographic image forming apparatus according to  claim 1 , wherein the processor is configured to:
 reduce an amplitude of a frequency component, which is in a region having a predetermined width in an axis direction corresponding to the first axis or the second axis of the first image, on the second image, compared to other components. 
 
     
     
       6. The tomographic image forming apparatus according to  claim 4 , wherein the processor is configured to:
 reduce an amplitude of a frequency component, which is in a region having a predetermined width from the first axis or the second axis DC component of the first image, on the second image, compared to other components. 
 
     
     
       7. The tomographic image forming apparatus according to  claim 6 , comprising:
 a filter having a distribution in which amplitudes in both ends of the predetermined width from the DC component are approximated to original values. 
 
     
     
       8. The tomographic image forming apparatus according to  claim 3 , wherein the processor is configured to:
 decrease the amplitude of the DC component to zero or smaller, or gradually approximate the amplitude of the DC component to zero. 
 
     
     
       9. The tomographic image forming apparatus according to  claim 1 , wherein the processor is configured to:
 reduce noise on the third image by applying a filter thereto or performing a threshold process thereon. 
 
     
     
       10. The tomographic image forming apparatus according to  claim 1 , wherein the processor is configured to:
 reduce noise on the third image by converting the third image into a frequency domain and applying a filter thereto or performing a threshold process thereon. 
 
     
     
       11. The tomographic image forming apparatus according to  claim 1 , wherein the processor is configured to:
 select a predetermined region of an original image in which the line data is arranged in the direction of the second axis; 
 reduce an amplitude of a DC component, which shows a zero frequency in the direction of the second axis on the original image, on an image obtained by converting the image in the predetermined region into a frequency domain, compared to other components; and 
 replace the predetermined region of the original image with an image obtained by inversely converting the image into an image in the spatial domain, 
 wherein the image obtained is the first image. 
 
     
     
       12. The tomographic image forming apparatus according to  claim 11 ,
 wherein the image in the predetermined region is an image where a region other than the predetermined region of the original image is set to have the lowest brightness value, and 
 the processor is configured to:
 extract the predetermined region from the image obtained by inversely converting the image into the spatial domain, and replaces the image in the predetermined region of the original image. 
 
 
     
     
       13. The tomographic image forming apparatus according to  claim 11 , wherein the processor is configured to:
 select a region within a predetermined distance from the shallowest position of the first axis on the original image, as the predetermined region. 
 
     
     
       14. The tomographic image forming apparatus according to  claim 11 , wherein the processor is configured to:
 select a region designated by a user as the predetermined region. 
 
     
     
       15. The tomographic image forming apparatus according to  claim 1 ,
 wherein brightness correction is performed after at least one filtering in the filtering processes. 
 
     
     
       16. A control method of a tomographic image forming apparatus which divides light output from a light source inside the apparatus into measurement light and reference light, and which generates a cross-sectional image of an imaging target based on light intensity of interference light obtained from reflected light obtained by emitting the measurement light to the imaging target and the reference light, the control method comprising:
 generating a second image by converting into a frequency domain a first image in which line data being generated based on the light intensity and having information in a direction of a first axis showing a depth direction of the imaging target is arranged in a direction of a second axis; 
 removing or reducing an artifact by performing filtering on the second image; and 
 generating a third image by inversely converting the second image into a spatial domain. 
 
     
     
       17. The control method according to  claim 16 , wherein the first image is converted into the second image by Fourier transform, cosine transform, or sine transform. 
     
     
       18. The control method according to  claim 16 , comprising:
 reducing an amplitude of a DC component which shows a zero frequency on the second image, compared to other components; 
 reducing an amplitude of a DC component, which shows a zero frequency in at least one axial direction on the first image, on the second image, compared to other components; 
 reducing an amplitude of a frequency component, which is in a region having a predetermined width in an axis direction corresponding to the first axis or the second axis of the first image, on the second image, compared to other components; and/or 
 reducing an amplitude of a frequency component, which is in a region having a predetermined width from the first axis or the second axis DC component of the first image, on the second image, compared to other components. 
 
     
     
       19. The control method according to  claim 18 , comprising:
 applying a filter having a distribution in which amplitudes in both ends of the predetermined width from the DC component are approximated to original values. 
 
     
     
       20. A non-transitory computer readable medium for a tomographic image forming apparatus which divides light output from a light source inside the apparatus into measurement light and reference light, and which generates a cross-sectional image of an imaging target based on light intensity of interference light obtained from reflected light obtained by emitting the measurement light to the imaging target and the reference light, the non-transitory computer readable medium having instructions operable to cause one or more processors to perform operations comprising:
 generating a second image by converting into a frequency domain a first image in which line data being generated based on the light intensity and having information in a direction of a first axis showing a depth direction of the imaging target is arranged in a direction of a second axis; 
 removing or reducing an artifact by performing filtering on the second image; and 
 generating a third image by inversely converting the second image into a spatial domain.